The Supreme Court says the bets are on. Yesterday, the court ruled that a 25-year-old law that had barred most states from legalizing sports betting is unconstitutional. It opens the door to legalize sports gambling across the country. NPR legal affairs correspondent Nina Totenberg reports.

NINA TOTENBERG, BYLINE: For the record, the Supreme Court, by a 6-3 vote, struck down the 1992 federal law because the court said that barring state legislatures from legalizing sports betting amounts to an unconstitutional commandeering of the state legislatures. Congress can outlaw sports betting on its own, the court said, but it can't achieve the same result by telling state legislatures what they can and cannot do. The federal law struck down by the court was known as the Bradley Act after its chief sponsor, Senator Bill Bradley of New Jersey, a onetime college and pro basketball great.

BILL BRADLEY: I think the court ignored the impact of their ruling on sport. I think they've turned every baseball player, basketball player, football player into a roulette chip. There's nothing to prevent betting on high school or even grade school games with this ruling.

TOTENBERG: Indeed, most experts on sports betting expect that a majority of the states will legalize sports betting in the next year or two. In some states, like New Jersey, which brought the legal challenge, officials expect that bets will start being taken in a matter of weeks.

ANDREW BRANDT: Gambling is a huge, huge fan-engagement tool.

TOTENBERG: Andrew Brandt is director of sports law at Villanova University. He points to research showing that the average NFL fan who's not a better watches 15 to 16 games a year, while the average NFL fan who is a better watches 45 to 50 games a year.

BRANDT: That kind of information is gold. It's gold. People are going to watch games they have no rooting interest for because cause of gambling.

TOTENBERG: Now the sports leagues are figuring out how to monetize all this. They're demanding a cut of the fees the states are charging. They're arguing further that the league should be paid for doing what they do now in Las Vegas for free, maintaining the integrity of the betting systems and working with law enforcement to spot cheating. They're looking at how to charge the fantasy leagues like DraftKings, which until now could only market fantasy games but soon will be making an estimated 10 to $20 billion a year more by taking bets on real games. The biggest problem facing sports betting is the very lucrative market for betting on college games. As John Wolohan, professor of sports law at Syracuse University, puts it...

JOHN WOLOHAN: The NCAA kind of throws the wrench in the works here.

TOTENBERG: That's because the risk of corruption is greatest when dealing with amateur athletes who will remain unpaid even as the colleges they play for get a cut of the gambling action. And then there's the Internet. Again, Villanova's professor Brandt.

BRANDT: The Internet - now we're talking about the great unknown because the real future in this, the inflection point for gambling is not what we know now, but it is in-game betting. That means you're going to be sitting at the stadium, at the arena, at the baseball diamond, and you're going to bet on the next pitch, the next play, the next basket, the next swing, and oh, my God. Think of the possibilities.